U.S. patent number 5,830,927 [Application Number 08/906,468] was granted by the patent office on 1998-11-03 for printing ink compositions, methods for making same and uses thereof.
This patent grant is currently assigned to Lehigh University. Invention is credited to Philippe Huwart, John W. Vanderhoff.
United States Patent |
5,830,927 |
Vanderhoff , et al. |
November 3, 1998 |
Printing ink compositions, methods for making same and uses
thereof
Abstract
Aqueous based printing ink compositions adapted for use in
gravure and flexographic printing on hydrophobic substrates are
prepared by combining a low-viscosity resin emulsion having an
average particle diameter of less than about 0.5 microns and
comprised of hydrophobic, moisture resistant, adherent resin
forming components with a pigment paste containing a water-soluble
polymer. The printing inks are substantially devoid of volatile
organic solvent.
Inventors: |
Vanderhoff; John W. (Bethlehem,
PA), Huwart; Philippe (Walhain, BE) |
Assignee: |
Lehigh University (Bethlehem,
PA)
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Family
ID: |
22861753 |
Appl.
No.: |
08/906,468 |
Filed: |
August 5, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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229557 |
Apr 19, 1994 |
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Current U.S.
Class: |
522/81; 522/84;
522/85; 106/31.75; 106/31.78; 106/31.88 |
Current CPC
Class: |
C09D
11/101 (20130101) |
Current International
Class: |
C09D
11/10 (20060101); C09D 011/10 (); C08F
002/50 () |
Field of
Search: |
;522/3,84,85,81
;106/2B,23R,23C,3A,31R |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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H304 |
July 1987 |
Vorrier et al. |
4101493 |
July 1978 |
Nakagawa et al. |
4177177 |
December 1979 |
Vanderhoff et al. |
|
Primary Examiner: Berman; Susan W.
Attorney, Agent or Firm: Leavitt; Samson B. Leavitt; Michael
A. Novack; Michael R.
Parent Case Text
This application is a Continuation of application Ser. No.
08/229,557 filed Apr. 19, 1994, now abandoned.
Claims
What is claimed is:
1. An aqueous printing ink composition substantially devoid of
volatile organic solvents, having a viscosity of about 10 to 50
poises and useful for gravure and flexographic printing on
hydrophobic smooth, non-porous plastic and metal substrates
prepared by:
A. dispersing a low molecular weight hydrophobic ultra-violet
curable vinyl functional oligomer in an aqueous medium in the
presence of an oil-in-water emulsifier-coemulsifier combination in
which the molar ratio of emulsifier to coemulsifier is about 4:1 to
1:4, and subjecting the resulting crude aqueous oligomer emulsion
to the action of comminuting forces sufficient to reduce the
average particle sizes of the oligomer below about 1 micron and
below the critical particle diameter which in practice will never
settle, and wherein
I. said emulsifier comprises a nonionic, anionic, cationic,
amphoteric or zwitterionic surfactant or any mixture thereof,
II. said coemulsifier comprises a water insoluble hydrocarbon or
hydrocarbyl alcohol, ester, ether, amine or halide containing an
aliphatic hydrocarbyl moiety of at least 8 carbon atoms, or any
mixture thereof, and
III. the aqueous oligomer emulsion comprises an effective amount of
a photo initiator/photosensitizer;
B. mixing a water insoluble pigment with water in the presence of a
water soluble polymeric grinding vehicle and grinding the mixture
to produce a ground pigment master batch paste,
C. mixing the aqueous oligomer emulsion from A with the said ground
pigment master batch paste, and
D. adding to the mixture from C about 1 to 10% by weight of the
printing ink composition of a water soluble or water reducible
polymeric thickener effective to adjust the rheology properties of
the final printing ink composition to sustain a rapid decrease in
viscosity with increasing rate of shear to a plateau value of about
205 poises at high shear rate of about 10.sup.-4 -10.sup.-3
reciprocal seconds followed by a corresponding increase in
viscosity upon cessation of the shear.
2. A composition as defined in claim 1 wherein there is present in
said oligomer emulsion a crosslinking polyethylenically unsaturated
monomer reactive with said oligomer.
3. A composition as defined in claim 2 wherein there is present in
said oligomer emulsion a monoethylenically unsaturated monomer
polymerizable under ultra-violet radiation.
4. A composition as defined in claim 3 wherein the emulsifier is
selected from mono C.sub.10 to C.sub.20 alkyl, tri lower alkyl
quaternary ammonium halides and C.sub.10 to C.sub.20 alkyl sulfates
and the coemulsifier is selected from C.sub.10 to C.sub.20
alkanols, esters, ethers, halides and amines, and aliphatic
hydrocarbons of at least 8 carbon atoms, the emulsifier and
coemulsifier each having molecular weights of less than about
2000.
5. A composition as defined in claim 4 wherein the oligomer,
polyethylenically unsaturated cross-linking agent and
monoethylenically unsaturated monomer content ranges from about 10
to about 50% by weight; the emulsifier combination content from
about 0.25 to about 5% by weight; the photo
initiator/photosensitizer content from about 0.5 to about 5% by
weight based on the weight of oligomers and monomers; the pigment
content from about 5 to 25% by weight; and including fron about 1
to 10% by of a water soluble polymeric thickener.
6. A composition as defined in claim 2 wherein the
polyethylenically unsaturated monomer comprises a di-, tri-, tetra-
or penta-acrylate.
7. A composition as defined in claim 6 including a
monoethylenically unsaturated monomer selected from the group
consisting of acrylates, methacrylates, vinyl esters and vinyl
pyrrolidone.
8. A composition as defined in claim 1 wherein the
emulsifier-coemulsifier combination comprises a sodium salt of a
C.sub.10 to C.sub.20 alkyl sulfate and a C.sub.10 -C.sub.20 alkanol
in a molar ratio of about 1:1 to 1:4.
9. A composition as defined in claim 8 wherein the said combination
comprises sodium lauryl sulfate and cetyl alcohol in a molar ratio
of about 1:4.
10. A composition as defined in claim 1 wherein the
emulsifier-co-emulsifier combination comprises a quaternary
ammonium halide and a C.sub.10 to C.sub.20 alkanol in a molar ratio
of about 1:1 to 1:4.
11. A composition as defined in claim 10 wherein the said
combination comprises hexadecyl trimethyl ammonium bromide and
cetyl alcohol in a molar ratio of about 1:4.
12. A composition as defined in claim 1 wherein the emulsifier
comprises a sodium C.sub.1 -C.sub.20 alkyl sulfate and the
coemulsifier comprises an aliphatic hydrocarbon of at least 8
carbon atoms in a molar ratio of about 1:1 to 1:3.
13. A composition as defined in claim 12 wherein the emulsifier
comprises sodium lauryl sulfate and the coemulsifier comprises
hexadecane in a molar ratio of about 1:3.
14. A composition according to claim 1 wherein said polymeric
thickener comprises an associative thickener containing a mixture
of water soluble or water reducible polymers, the molecules of
which associate more with each other than with the functional
groups on the latex particles in the oligomer emulsion to give said
printing ink composition said rheological properties.
15. An aqueous printing ink composition substantially devoid of
volatile organic solvents, having a viscosity of about 10 to 50
poises and useful for gravure and flexographic printing on
hydrophobic smooth, non-porous plastic and metal substrates,
prepared by:
A. mixing a water insoluble pigment with water in the presence of a
water soluble polymeric grinding vehicle and grinding the mixture
to produce a ground pigment master batch paste,
B. mixing the ground pigment master batch paste with
I. an aqueous emulsion of ion molecular weight hydrocarbon resin
oligomers prepared by cationic polymerization of a mixture of
C.sub.4 to C.sub.7 hydrocarbons, and further containing a
photoinitiator and a cross-linking polyethylenically unsaturated
monomer, or
II. an aqueous butadiene/styrene copolymer latex emulsion
polymerized to about 60% conversion and containing about one double
bond for each butadiene unit, and further containing a
photoinitiator and a cross-linking polyethylenically unsaturated
monomer, and
C. adding to the resulting mixture about 1% to 10% by weight of the
printing ink composition of a water soluble or water reducible
polymeric thickener effective to adjust the rheology properties of
the final ink composition to sustain a rapid decrease in viscosity
with increasing rate of shear to a plateau value of about 2-5
poises at high shear rate of 10.sup.-3 to 10.sup.-4 reciprocal
seconds followed by a corresponding increase in viscosity upon
cessation of the shear.
16. A composition according to claim 15 wherein said polymeric
thickener comprises an associative thickener containing a mixture
of water soluble or water reducible polymers, the molecules of
which associate more with each other than with the functional
groups on the latex particles in the water insoluble polymer
emulsion to give said ink said rheology properties .
Description
The present invention relates to new and improved printing ink
compositions and methods for making and using same, and in
particular to ultra-violet radiation curable inks particularly
suitable for use on plastic materials and which are ecologically
friendly. More specifically, the present invention relates to
printing ink compositions which are suitable to print by gravure or
flexography on a variety of flexible substrates from metal foils
(e.g. aluminum) to plastic films, and especially hydrophobic
plastic film substrates such as polyethylene and other nonporous
non-polar plastic materials. The printing inks are substantially
devoid of volatile, organic solvents and the ink films formed on
the substrates are extremely resistant to water, and have excellent
adherence to the base material.
BACKGROUND OF THE INVENTION
Printing inks for use in flexographic and gravure printing have
generally, for the last 60 years and almost predominantly for the
earlier years in this period, utilized volatile solvent-based ink
formulations following the invention by Adolph Weiss in the
mid-1920's of the closed ink fountain (U.S. Pat. No. 1,631,169)
which literally revolutionized rotogravure printing by opening the
way to use much faster drying inks and thus much higher printing
speeds.
Increased awareness of the detrimental effects of the rapid sweep
of the industrialized world for power, money and higher levels of
the "standard of living" on the environment and health and safety
of all living things has, as we all know, led to increased
governmental restrictions on all facets of our economy. Among these
have been severe limitations on what can be vented to the
atmosphere and in the context of this invention, on the amount of
organic solvent vapor which can be vented. This has challenged
those in the field of printing inks to lower and probably
eventually totally eliminate any organic solvents in all printing
inks and pastes. The response to this challenge has been the
development of solventless inks; low-smoke low-odor inks, which can
be used to replace the heatset inks; air-drying inks covered with a
protective layer of alcohol-soluble polymer; thermally-catalyzed
inks, which use blocked acid catalysts that become unblocked at
high temperature; inks cured by infrared, ultraviolet light, and
electron beam radiation; and water-based inks.
Solvent incineration systems have been developed to burn off the
emitted solvents; however, these require additional fuel (natural
gas or oil) and high temperatures. Solvent recovery units have also
been developed to absorb, condense or otherwise recover the
solvent; however, the solvent recovery is only partial, and some
solvent escapes to the atmosphere. Solvent incineration has been
used to burn off solvents from the paste inks used for lithographic
and letterpress printing, and solvent recovery has been used to
recover the solvent from the liquid inks used for flexographic and
gravure printing. These latter inks often comprise 80% solvent and
20% pigment/binder mixture, so that four lbs. of solvent are vented
to the atmosphere for each lb. of ink printed. Also, the solvent
recovery units often allow some solvent to escape to the
atmosphere. Thus, even the relatively small proportion of solvent
that escapes is substantial in view of the considerable quantities
of printing inks used.
A large volume of plastic film and foil is printed for packaging
applications such as bread wrap. The inks used comprise polyamide,
nitrocellulose, and other cellulosic polymer vehicles formulated
with pigments (20%) and dissolved in organic solvents (80%).
Generally, the plastic films are treated with corona discharge,
exposed to solvents or flames, or etched with acids to form surface
functional groups that enhance the adhesion of the inks. When
printed, these inks give adequate, but not outstanding adhesion to
the plastic film and foil, even at high humidity.
At about the turn of this decade, the Environmental Protection
Agency asked printers and converters who use flexographic and
gravure printing to substitute water-based inks for the
solvent-based inks presently used. The current water-based inks
work reasonably well for printing on absorbent substrates such as
paper, paperboard, boxboard, and cardboard, and are widely used for
these purposes; however, these inks do not adhere well to the
smooth, nonporous, nonpolar plastic film and foil substrates;
typically, the adhesion of the ink is poor, especially after
exposure to high humidity. Thus, there were strong efforts to
develop water-based inks that adhere well to these substrates.
Water-based inks for flexographic and gravure printing have been
used for over thirty years but all contain from about 10% to 20% of
a water-miscible solvent. Typically, the pigments are ground in a
pigment grinding vehicle; the pigment dispersion thus formed is
diluted ("let down") in another vehicle. The pigment grinding
vehicles are usually water-soluble polymers; the letdown vehicles
are usually water-reducible (water-dispersible) polymers prepared
by emulsion polymerization using high concentrations of
carboxyl-containing monomers, followed by neutralization. The
water-soluble polymer is required for good printability; the inks
will not transfer properly from one roll to another, or from a roll
to the printing plate, if a water-soluble polymer is not present.
The latex is required to give an ink film with good film
properties, particularly toughness. The latexes comprise
high-molecular-weight polymers that give good film properties; the
solution polymers are limited to low-molecular-weight polymers
because of the viscosity requirements. Again, as described above,
these inks performed reasonably well on absorbent substrates but
not so on smooth, nonporous, non-polar plastic film and foil
substrates.
Prior art illustrative of the foregoing ink and coating
compositions include the following: U.S. Pat. No. 3,048,530
describes a polyvinyl acetate latex paint, U.V. light is used
during polymerization to accelerate the formation of the latex
product. Photopolymerizable printing ink compositions are described
in U.S. Pat. Nos. 3,801,329; 4,003,868; 4,014,771; 4,035,320;
4,056,453; and 4,271,258 and U.S. Statutory Invention Registration
H304 (Published Jul. 7,1987). None of the compositions shown in
these patents is aqueous-based. While they are volatile
solvent-free, except for Publication H304, none teaches the
composition as being useful in flexographic printing.
Significantly, the H304 disclosure teaches the great desirability
of the use of a primer coating of polyvinylidene chloride or a
solvent-reduced resin solution (e.g. polyester, vinyl, acrylic
ester, or cellulose acetate butyrate). Water-based, radiation
curable compositions are described in U.S. Pat. No. 4,339,566
(textile printing); U.S. Pat. No. 4,360,541 (self-pigmented
protective coatings) and U.S. Pat. No. 5,045,435 (for dip coating
and screen printing). None of these water-based compositions is
taught as having utility in flexographic printing.
U.S. Pat. No. 5,028,262 discloses ink compositions which are
aqueous dispersions of a water-dispersible polymer, a disperse dye
and a dihydroxy benzophenone, the latter functioning to stabilize
the dye with respect to precipitation.
OBJECTS OF THE INVENTION
It is therefore, a primary object of this invention to provide ink
compositions which are water-based and volatile organic
solvent-free and which yield strong, adherent, water-resistant
printed films on hydrophobic, flexible substrates.
It is another object of this invention to provide aqueous-based,
solvent-free printing inks adaptable to give strong, adherent and
water-resistant films on smooth, non-porous,non-polar flexible
metal foil and plastic film substrates.
It is still another object of this invention to provide water-based
and organic solvent-free printing inks which are ultra-violet light
curable to give strong, adherent and water-resistant films on metal
and hydrophobic plastic substrates.
It is a further object of this invention to provide processes of
making and using the foregoing compositions.
Other objects and advantages will appear hereinafter as the
description proceeds.
SUMMARY OF THE INVENTION
The objects of this invention are attained by providing printing
ink compositions which are ultra-violet radiation curable
water-based formulations, substantially devoid of volatile, organic
solvents, which have a viscosity of from about 10 to 50 poises, a
generally necessary criterion for the use of inks in gravure and
flexographic printing processes, and which include a relatively
low-molecular weight hydrophobic vinyl-functional polymer
(oligomer) binder which is curable by ultra-violet radiation, using
conventional photo initiators, to a water-insoluble, hydrophobic
form. The oligomer latex (emulsion) is provided in very stable form
by direct emulsification of the oligomer in water using an
emulsifier-coemulsifier combination whereby the emulsified
particles are substantially below one micrometer in size [one
micron (.mu.)] and below the critical particle diameter which
corresponds to a particle diameter which in practice will never
settle. One criterion for settling as discussed by Overbeek in
"Colloid Science, Vol. 1" H. R. Kruyt, Editor, Elsevier, Amsterdam,
1952 p.80, is that a sedimentation rate of 1 mm in 24 hours
according to Stoke's Law will be offset or nullified by the thermal
convection currents and Brownian motion within the sample. Using
Stoke's equation to determine V (rate of settling): ##EQU1##
wherein a=radius of sphere (e.g. particle), d.sub.1 and d.sub.2
=densities of the sphere and medium respectively, .eta.=the
coefficient of viscosity, and g is the acceleration due to gravity
(free fall).
V will be in cm/sec if g is in cm per sec.sup.2, a in cm, d.sub.1,
and d.sub.2 in g per cm.sup.3 and .eta. in degree-sec per cm.sup.2
or poises; for polystyrene which has a density of 1.050 g/cm.sup.3,
the critical diameter is 0.65.mu..
The emulsifier-coemulsifier direct emulsification technique such as
described in U.S. Pat. No. 4,177,177 (Vanderhoff et al), which is
hereby incorporated by reference, readily produces particle sizes
averaging well below 0.65.mu., e.g. less than about 0.5.mu.,
preferably about 100-400 nm (nanometers). The provision of latices
with particle sizes this small not only results in outstanding
stability of the latex per se but also of the finally formulated
ink, and as a further great advantage, one is enabled to effect
excellently coalesced films. A further advantage, in the context of
coalescing films of the instant aqueous systems, is that the
water-air interfacial tension (which can be as high as 72 dynes/cm
in pure water and as high as 35-dynes/cm in the presence of excess
surfactant) is directly related to the force involved in causing
particles to coalesce into film and is much greater than organic
solvent solution-air interfacial tensions, (e.g. 10-15 dynes/cm).
Thus because of these greater forces, more viscous oligomer binders
can be used.
An additional component of the resin latex which it is generally
preferred to employ to effect the strongest and most
deformation-resistant continuous phase of the printed ink film is a
cross-linking, polyfunctional monomer.
A further optional but often desirable component is a
monofunctional monomer. Often one may use either a cross-linking
monomer or a monofunctional monomer (or both).
The polymer emulsification process using the
emulsifier-coemulsifier combination is conveniently carried out as
described in U.S. Pat. No. 4,177,177. A solution of the resin(s) is
stirred into the water phase containing the surfactant/emulsifier
mixture. This produces a crude emulsion with 1-100.mu. diameter
droplets. The crude emulsion is then subjected to the action of
comminuting forces such as homogenization or ultra-sonification
which results in particle diameters of generally 0.1 to 0.4
microns. The solvent used to form the resin solution is removed by
vacuum steam distillation. To this latex is added the necessary
photo initiator to provide the free radicals to "set" the resin
composition to its final insoluble form. The well-known and
conventional photo initiators are available for this function. This
hydrophobic oligomer emulsion is later referred to and/or employed
as the "let down" vehicle.
The colorants used in the present compositions are water-based
insoluble pigments or dyestuffs which are generally prepared by
grinding (i.e. dispersing) the pigment in water using a water
soluble polymeric grinding vehicle; then "letting down" this
pigment dispersion with the "letdown" vehicle i.e. the U.V. curable
hydrophobic oligomer latex emulsion; a water-soluble or
emulsifiable polymer (thickener) is added in small concentrations,
to control the rheological properties of the ink.
Other adjuvants may be added to the pigment batch to improve
properties, e.g. mar resistance. Surprisingly, adding a aqueous wax
emulsion to the pigment batch before adding the U.V. radiation
curable resin binder formulation results in a marked improvement in
mar resistance of the cured ink film on the hydrophobic substrate
in contra-distinction to the results obtained when a wax emulsion
is added to a conventional latex coating formulation. In the latter
instance, adhesion of the latex-derived film is significantly
adversely affected whereas in the present invention it is found
that by curing the resin binder in situ, the adhesion of the ink
film is not so affected.
A further surprising benefit of the present compositions lies in
the fact that in the printing process it is not necessary to
pre-dry the ink on the substrate as a separate step before curing
the ink with ultra-violet radiation. In the curing step it is
feasible with the conventional equipment now used (e.g. 200
watt/inch Hanovia Lamps) to effect water removal (i.e. drying) and
"curing" of the film in a single step.
A further benefit deriving from the unique ink compositions of the
present invention lies in the attainment of high-strength film with
minimum tendency to delaminate from the underlying flexible plastic
film. Since the strength of the cured ink films depends upon the
resin binder used and the efficiency of the particle coalescing
process, it is patently clear that the strength of the binder per
se depends on its composition as well as the degree of curing.
Increasing binder strength as by chemical composition,
cross-linking, etc. would in most cases decrease flexibility and
could in an extreme case increase delamination from the substrate.
Since this tendency is lowered as the ink film thickness decreases
and since the printing ink compositions of the present invention
enable production of ink printing and coating thicknesses generally
as low as about 2 microns, we find this "catch 22" situation to be
neutralized with the present compositions and printing processes
using them.
DETAILED DESCRIPTION OF THE INVENTION
The primary, film-forming ("binder") resins of the printing ink
composition of this invention are low-molecular weight hydrophobic
oligomers having a molecular weight of from about 400 to 10,000 and
are generally fluid-to-viscous liquids with viscosities ranging up
to about 25000 cps @ 25.degree. C. Suitable oligomers include as a
preferred group--vinyl functional oligomers, hydorcarbon based
oligomers and derivatized hydrocarbon oligomers. The
vinyl-functional oligomers are generally acrylic or methacrylic
acid esters of epoxide resins, urethanes, polyesters and alkyds.
Specific products include amine-modified diacrylates of bis-phenol
A type epoxide resins (e.g. Novacure 3600, MW 548, 1300 cps
viscosity at 65.degree. C.); acrylated epoxy resins (e.g. Novacure
3700-25R, MW 524, viscosity 14000 cps @ 25.degree. C., similar to
Novacure 3600 but including 25% by wt of tripropyleneglycol
diacrylate); acrylic esters of urethane, e.g. aliphatic urethane
diacrylate (Ebecryl 230); aliphatic urethane diacrylate diluted 10%
with tetraethylene glycol diacrylate (TTEGDA) (Ebecryl 4830);
multi-functional aromatic urethane acrylate (Ebecryl 220); Ebecryl
3700 with 20% trimethylol-propane triacrylate (TMPTA).
It should be noted that the first commercial oligomers of these
types were identified as "Hi-Tek", which was changed to "Novacure",
then "Radcure", and currently "Ebecryl" (since about May 1993).
For some other specific urethane acrylates see, U.S. Pat. No.
4,339,566, and U.S. Statutory Invention Registration #H304, which
are incorporated by reference. Other specific epoxy acrylates are
disclosed in the prior art. Among the above types of preferred
oligomers, an illustrative structural formula is represented by the
following for Novacure 3700-25R: ##STR1## wherein n is the value
needed to provide a MW of 524.
Further useful but only illustrative oligomers are Ebecryl 220--a
multi-functional aromatic urethane acrylate; Ebecryl 810--a multi
functional polyester acrylate; Ebecryl 770--an acid functional
polyester acrylate diluted 40% with Hydroxyethyl methyl diacrylate
(HEMA), Escorez EC 346R (Exxon) a hydrocarbon resin prepared from a
petroleum fraction of C.sub.4 -C.sub.7 hydrocarbons (70%
aliphatic--30% aromatic) cationically polymerized with residual
double bonds--brittle yellow solid, density about 0.6 g/cm.sup.3 ;
butadiene-styrene latex; carboxy-terminated polybutadiene oligomer,
MW5600--viscous liquid, soluble in dichloromethane (Scientific
Polymer Products).
The aforementioned hydrocarbon resin, butadiene-styrene latex and
carboxy-terminated polybutadiene oligomer differ from most of the
previously described oligomers in not being acrylic acid esters of
oligomeric epoxide resins, urethanes, polyesters, alkyds and the
like, and in containing somewhat less reactive residual double
bonds. Their use in this invention as substitutes or equivalents of
the said "vinyl-functional oligomers" is described below in
Examples 7, 8, 9 and 11.
The emulsifiers used to prepare the oligomer emulsion (latex) may
comprise any of the known non-ionic, anionic, cationic, amphotenic,
zwitterionic, etc. surfactants as for example fully described in
U.S. Pat. No. 3,762,859, column 3, line 6 to column 8, line 15
which description is incorporated herein by reference thereto.
Preferred are the anionics, particularly the alkali (Na, K, Li)
C.sub.10-20 alkyl sulfates such as sodium lauryl sulfate and sodium
hexadecyl sulfate; the cationics, particularly the quaternary
ammonium halides such as C.sub.10 to C.sub.20 alkyl (e.g.
octadecyl) piperidine bromide and C.sub.10 to C.sub.20 alkyl (e.g.
hexadecyl) tri lower (C.sub.1 to C.sub.4) alkyl (e.g. methyl)
ammonium bromide; and the nonionics, particularly the exthoxylates
of higher M.W. (>C.sub.8) reactive hydrogen-containing
compounds, e.g. C.sub.10-20 alkanols, C.sub.8-18 alkyl phenols and
C.sub.10-20 fatty acids with from about 3 to 50 or more (e.g. 5-50;
5-60 etc.) moles of ethylene oxide (E.O.) per mole of such compound
(alcohol, acid or phenol). Specific examples are octylphenol and 40
E.O.; lauryl alcohol and 12 E.O., tall oil fatty acid and 20 E.O.
Generally, any oil-in-water emulsifying agent is satisfactory.
The co-emulsifier may be a hydrocarbon, alcohol, ester, amine,
halide, ether, etc. Preferred are those with an aliphatic
hydrocarbyl-containing moiety of at least 8 carbon atoms,
water-insoluble (less than 10.sup.-3 liter of water), with
molecular weights not exceeding about 5000, preferably 2000 and
more preferably from about 110 to 500, especially alkanes and
alkanols. These compounds may be aliphatic hydrocarbons such as
n-octane, n-decane,n-octadecane, eicosane, 1-dodecene, 3-octyne,
dodecylcyclohexane, tetradecanol, hexadecanol (cetyl alcohol),
1-hexaeicosanol, cetyl acetate, hexadecylamine, octadecylamine,
hexadecyl chloride, octyl ether, cetyl ether, methyl octanoate,
octyl caproate, ethyl stearate, glyceryl tristearate, coconut oil,
olein and the like.
The cross-linking compounds (polyfunctional monomers) include by
way of illustration only, trimethylol propanetriacrylate (TMPTA),
pentaerythritol tetracrylate (PETA), hexanediol diacrylate (HDODA),
tetraethylene glycol diacrylate (TTEGDA), tripropylene glycol
diacrylate (TPGDA), 1,4-butanediol diacrylate (BDODA), glyceryl
propoxylate triacrylate (GPTA), divinyl benzene and trialkyl
cyanurate.
Any monofunctional monomer may be used where it's use is indicated
or desirable. Examples include 2-ethylhexyl acrylate, decyl
acrylate, N-vinyl-2-pyrrolidone and vinyl acetate. Many, many
others may be used but constraints of odor, volatility and
reactivity make many of these others less desirable.
Mixtures of different "binder" resins, polyfunctional and
monofunctional monomers may, of course, be used as well.
The photo initiators needed to effect curing, of the total resin
system are well known and include inter alia, acetophenones and
benzophenones, xanthones, and benzoin derivatives. Reference is
made to U.S. Pat. Nos. 3,801,329; 4,003,868 and 4,014,771 and U.S.
Statutory Invention Legislation H304 published Jul. 7, 1987 for
illustrative specific initiators, and their disclosures are herein
incorporated by reference thereto.
The following photoinitiators besides the
2,2'-diacetoxyacetophenone (Aldrich) have been tested in the
formulations of this invention in 1-2% concentration based on oil
phase:
1. KIP 100 F (Fratelli Lamberti spa);
2. KIP 37 (Fratelli Lamberti spa);
3. Irgacure 500 (Ciba-Geigy);
4. Irgacure 369 (Ciba-Geigy);
5. Darocur 4665 (Merck).
All of these photoinitiators showed positive results. The Irgacure
369 gave a fast curing rate, but, with the clear resins, developed
a yellow color. Some of these photoinitiators were difficult to
incorporate into the miniemulsion particles. In these cases, the
photoinitiator was emulsified in water using Triton X-200
(octylphenol-polyoxyethylene adduct (4 moles ehtylene oxide) with a
sulfate endgroup; Rohm & Haas); this emulsion was subjected to
untrasonification and then added to the miniemulsion.
The concentration of the components of the resin emulsion may vary
widely depending on the nature of the binder(s), the intended
substrate and the pigment paste which is used. Generally the
oligomer binder(s) content may vary from 5 to 60% by weight,
preferably 10 to 50% by weight and more preferably 15 to 40% by
weight based on the weight of the emulsion composition.
Illustrative concentrations are (1) 19% Acrylated epoxy viscosity
1300 cps at 65.degree. C.; (2) same as (1) plus 5% TMPTA
(trimethylol propane:triacrylate); (3) same as (2) plus 15%
2-ethylhexyl acrylate (4) 22% acrylated epoxy (viscosity 14000 cps
@ 25.degree. C.; (5) same resin as (4) at 20% plus 5% TMPTA ; (6)
same as (5) plus 15% 2-ethylnexyl acrylate; (7) hydrocarbon
(C.sub.4 to C.sub.7 --70% aliphatic 30% aromatic) resin--40%; (8)
75/25 butadiene-styrene copolymer--18%; (9) same as (1) plus 4%
tetraethylene glycol diacrylate; (10) same as (9) plus 10% vinyl
acetate; (11) same as (9) plus 12% N-vinyl-2-pyrrolidone; (12) same
as (4) plus 5% divinylbenzene; (13) same as (7) plus 2%
divinylbenzene; and (14) same as (8) plus 15% 2-ethylhexyl
acrylate.
The surfactant emulsifier(s) (EM) content used in the emulsion
preparation may vary from about 0.1% to about 15%; preferably about
0.2 to about 10% and more preferably from about 0.25 to about 5% by
weight based on the weight of water. The amount of co-emulsifier
(Co-EM) will generally be related to the amount of surfactant
emulsifier with suitable molar ratios of Co-EM to EM within the
range of about 1:4 to 4:1. Some highly preferred combinations are
sodium lauryl sulfate/Cetyl alcohol in a 1:4 Molar Ratio (about
1:3.4 wt. ratio) and sodium lauryl sulfate/hexadecane in a 1:3
molar ratio (weight ratio about 1:2.8).
The amount of photo initiator may vary from about 0.5 to about 10%
by weight based on the weight of oligomer(s) and monomer(s), and
preferably from about 1 to about 5% by weight.
It is often desirable to add a water soluble polymer to the resin
emulsion, to promote adhesion to the substrate, prevent coagulation
of the pigment paste formulation which is to be added to the
emulsion to prepare the final printing ink, prevent pigment
settling, enhance pigment dispersion and adjust viscosity of the
final printing ink. Suitable polymers include polyvinyl
pyrrolidone, polyacrylamide, solubilized acrylic acid-vinyl
acetate/vinyl alcohol inter polymers and the like. The selection of
the water soluble polymer will be guided by the substrate with
amounts varying from about 1 to about 20% by weight based on tile
weight of the emulsion with about 5 to about 15% preferred, e.g.
5%, 10%, 12% and 15%.
The second major component of the printing ink is, of course, the
pigment which can be any pigment whatsoever and literally thousands
are available. The pigment pastes are prepared in general,
illustratively, using three steps:
1. Neutralization and solubilization of the grinding vehicle;
2. Addition of the pigment to the solution of grinding vehicle;
3. Grinding of the pigment dispersion in a sand mill.
The grinding vehicles were generally low-molecular-weight hard
acrylic polymers, e.g., Joncryl 678. The composition of this
polymer probably comprised a copolymer of a carboxyl-containing
monomer with a hard monomer, e.g., styrene or alpha-methylstyrene.
These copolymers, often sold as a powder or flake, were mixed with
an aqueous solution of ammonia or an organic amine to neutralize
the carboxyl groups and solubilize the copolymer. The resulting
solution or dispersion was then used as the grinding vehicle.
The dry, powdered pigment was added stepwise with stirring to the
solution or dispersion of the grinding vehicle, and this dispersion
was homogenized into a smooth paste, called the pigment
masterbatch.
This pigment masterbatch was then ground in a sand mill (Coball
Mill, Fryma AG, Rheinfelden, Switzerland), which used glass or
zirconium beads of about 2.0-2.5 mm diameter to grind the
pigments.
The fineness of grind was measured using a NPIRI Production
Grindometer grind gauge. This comprised a rectangular steel block
with a tapered trough, ranging in depth from 0 to 25 micrometers. A
sample of dispersion was placed in the deep end of the trough and
drawn down with a steel drawdown blade. Pigment aggregates of a
size equal to the depth of the trough were caught under the blade
and made a "scratch" in the dispersion. The dispersions were rated
according to the number and size of these aggregates.
The above described hydrophobic oligomer emulsion was then added as
let-down vehicle to the resulting ground pigment master batch. A
water soluble polymeric thickener (1-10% of final ink) must be
added to the pigment masterbatch/let-down vehicle mixture to adjust
the rheology properties of the final ink to sustain a rapid
decrease in viscosity with increasing rate of shear to a plateau
value of about 2-5 poises at high shear rate of about 10.sup.3
-10.sup.4 reciprocal seconds, followed by a corresponding increase
in viscosity (e.g. to about 10,000 poises) upon cessation of the
shear. This polymer can be a solution polymer or a water-reducible
polymer because the thickener functions according to its
interactions with itself and the colloidal pigment and latex
particles. Its molecular weight can range from very low (e.g.,
1,000-2,000) to very high (over 200,000). Without this thickener
vehicle, the final inks did not wet the substrate, i.e. they tended
to dewet and crawl and retreat after application to the plastic or
metal flexible, non-porous, non-polar hydrophobic substrate with a
wire-wound rod or Pamarco handproofer (poor drawdowns or
rollouts).
Illustrative commercially available water-soluble polymers for this
thickening purpose include S. C. Johnson's Jonacryl 67, 537, 678,
8050, 8051, SCX-7630; Varnishes 8866 and 9562; Rohm & Haas
Primal E-1941 and Enorex AG's Elotex 2030.
The amount of pigment in the printing ink may obviously vary but
generally inks are formulated to about 5-25%, preferably 10-20%, by
weight of pigment with about 13% by weight being a generally used
level.
The following examples will serve to illustrate the present
invention without being deemed limitative thereof. Parts and
proportions referred to herein and in the appended claims are by
weight unless otherwise indicated.
EXAMPLE 1
A composition of the following ingredients is prepared:
______________________________________ Ingredient Parts by Weight
______________________________________ Water 60.00 Novacure 3600
19.20 Trimethylolpropane triacrylate crosslinking monomer 4.80
Toluene solvent 16.00 Sodium lauryl sulfate emulsifier 20 mM* Cetyl
alcohol co-emulsifier 80 mM* 2,2.sup.1 -diethoxyacetophenone photo
initiator 1.0%** ______________________________________ *based on
water **based on prepolymer/polyfunctional monomer mixture
The general production procedure involves the initial preparation
of the toluene solution of the epoxide resin and triacrylate cross
linking monomer. A separate aqueous emulsifier solution is prepared
(water and sodium lauryl sulfate and cetyl alcohol agitated at
70.degree. C. for 2 hours and then sonified for 2 minutes at a
power setting of 7 (50% duty cycle) in a Branson Sonifier Disruptor
W-350). This aqueous solution is then mixed with the toluene
solution using a magnetic stirrer for 1 hour and further sonified
for 2 minutes similarly as done separately for the aqueous
emulsifier portion. The toluene is then removed by vacuum steam
distillation. The average droplet size in the emulsion is less than
0.3 microns.
EXAMPLE 2
Ink formulations (A to MM) are prepared as shown in Table A using
Emulsions as prepared in Example 1. The Table indicates
illustrative substrates and pigment pastes. The inks are drawn down
on the "velvet" side of polycarbonate films, cured by ultraviolet
light, and the adhesion measured using a simple and acceptable
Scotch Tape Test, i.e., by pressing the tape on the cured ink film
and pulling it off; the failure of the ink to separate from the
polycarbonate film is indicative of good adhesion. The test is
repeated after aging the sample for three days at 100% relative
humidity. All of the combinations on polycarbonate show good
adhesion.
The polypropylene films are preferably treated with corona
discharge as are the low and high density polyethylene films before
application of the ink film. This is conventional in industrial
coating practice since the technique enhances adhesion ostensibly
through the generation of functional groups on the polymer film.
The usual practice is to treat the film immediately before coating
since the treatment is not permanent. All printings on the
polypropylene and the high and low density polyethylene films give
satisfactory results.
TABLE A
__________________________________________________________________________
Composition of Printing Inks Parts by Weight Plastic Film Polymer
Aqueous Water- Substrate Emulsion Pigment Paste Soluble Polymer
__________________________________________________________________________
A Polycarbonate 49.5 Red 9045 45.0 Primal E-1941 5.5 B
Polycarbonate 21.8 White 9335 75.8 Varnish 9562 2.4 C Polycarbonate
36.0 Black 9366 60.0 Varnish 9562 4.0 D Polycarbonate 45.0 Red 6754
50.0 Primal E-1941 5.0 E Polycarbonate 45.0 Red 9563 50.0 Primal
E-1941 5.0 F Polycarbonate* 44.5 Carmin 9564 50.6 Primal E-1941 5.0
G Polycarbonate 35.0 Black 9565 61.2 Joncryl 537 3.4 H
Polycarbonate 52.0 Red 8049 42.0 Primal E-1941 6.0 I Polycarbonate
55.0 Blue 9175 28.0 Primal E-1941 7.5 Varnish 8866 9.5 J
Polycarbonate 50.5 Blue 7287 44.0 Primal E-1941 5.5 K Polycarbonate
52.0 Yellow 9184 42.0 Primal E-1941 6.0 L Polycarbonate 47.0 Carmin
9043 48.0 Primal E-1941 5.0 M Polycarbonate 36.0 Black 9042 60.0
Primal E-1941 4.0 N Polycarbonate 50.5 Blue 6755/N 44.0 Primal
E-1941 5.5 O Polycarbonate 59.5 Green 6876 34.0 Primal E-1941 6.5 P
Polycarbonate 45.0 Red 9563 50.0 Primal E-1941 5.0 Q Polypropylene
21.8 White 9335 75.8 Joncryl 8050 9.6 R Polypropylene 52.0 Red 8049
42.0 Primal E-1941 6.0** S Polypropylene 45.0 Red 6754 50.0 Joncryl
537 5.0 T Polypropylene 55.0 Blue 9175 28.0 Varnish 8866 9.5
Joncryl 537 7.5 U Polypropylene 50.5 Blue 7287 44.0 Joncryl 537 5.5
V LD-polyethylene 38.5 White 9335 48.1** Joncryl 8050 9.6 W
LD-polyethylene 50.2 Red 8049 40.4** Joncryl 8050 5.6 X
LD-polyethylene 38.5 Red 67543 48.1** Joncryl 8050 9.6 Y
LD-polyethylene 52.9 Blue 9175 26.9** Varnish 8866 9.1 Joncryl 8050
7.2 Z LD-polyethylene 48.5 Blue 7287 42.3** Joncryl 8050 5.4 AA
HD-polyethylene 38.5 White 9335 48.1** Joncryl 8051 9.6 BB
HD-polyethylene 50.2 Red 8049 40.4** Joncryl 8051 5.6 CC
HD-polyethylene 38.5 Red 6754 48.1** Joncryl 8051 9.6 DD
HD-polyethylene 48.5 BLue 7287 42.3** Joncryl 8051 5.4 EE
HD-polyethylene 34.6 Black 9366 57.7** Joncryl 8051 3.8 FF
HD-polyethylene 56.0 Yellow 9184 32.0**** Joncryl 8051 6.2 GG
HD-polyethylene 56.6 Orange 9185 32.4** Joncryl 8051 6.3 HH
HD-polyethylene 34.4 Black 9042 57.3** Joncryl 8051 4.5 II
HD-polyethylene 33.6 BLack 9565 58.8** Joncryl 8051 3.8 JJ
HD-polyethylene 48.1 Blue 6755/N 42.0** Joncryl 8051 6.1 KK
HD-polyethylene 57.1 Green 6876 32.7** Joncryl 8051 6.3 LL
HD-polyethylene 43.3 Red 9563 48.1** Joncryl 8051 4.8 MM
HD-polyethylene 47.6 Carmin 9564 38.1*** Joncryl 8051 9.5
__________________________________________________________________________
LD polyethylene = low density polyethylene HD polyethylene = high
density polyethylene *or Joncryl 537 coalesced with Dowanol DPM
(diproplyene glycol methyl ether) **+3.8 pts W8853 aqueous wax
emulsion containing 28.5% water ***+4.8 pts W8853 aqueous wax
emulsion containing 28.5% water ****+5.8 pts W8853 aqueous wax
emulsion containing 28.5% water
The following Table B gives by way of illustration only the
compositions of some of the aqueous pigment pastes
(pigment/grinding vehicle) useful and specified in the examples and
description herein.
TABLE B ______________________________________ Paste Color Number
Composition ______________________________________ White 9335 46.0%
TiO.sub.2 pigment 2063 (Kronos) 11.0% Joncryl 678 9.5% Joncryl 90
Yellow 9184 31.0% Yellow 73 Acetanil 7312 (Cappelle) 16.0% Joncryl
678 Orange 9348 29.0% Orange 13 Diacetanil 1323 (Cappelle) 16.0%
Joncryl 678 Red 9563 26.0% Lake Red 153:1 5310C (Cappelle) 12.5%
Joncryl 678 7.0% Joncryl 90 Red 8049 32.0% Red 48:2 Eljon Rubine
2BRC (European Colour) 11.0% Joncryl 678 Carmine 9564 17.0% Rubine
Red 57:1 4BP (European Colour) 8.5% Lake Red 53:1 5316C (Cappelle)
12.5% Joncryl 678 6.5% Joncryl 90 Fanal Rose 6754 20.0% Fanal Rose
CF D 4810 (BASF) P Red 169 12.0% Joncryl 678 Phthalo 9175 46.0%
Microfast SMFI Blue 15:3 (Toyo Ink) Blue 12.0% Joncryl 678 Alkali
Blue 7287 18.2% Powdura Blue AP3600 Blue 19 (Sherwin Williams)
16.5% Joncryl 678 Violet 6755N 18.2% Violet lumiere 2744 P. Violet
(Cappelle) 16.5% Joncryl 678 Green 6876 38.0% Phthalo Green D-8730
(BASF) P Green 7 13.0% Joncryl 678 Black 9565 24.0% Printex 30
11.0% Joncryl 678 6.0% Joncryl 90 Black 9042 24.0% Printex 30
(degussa) 13.5% Joncryl 8004 Black 9368 25.0% Spezialschwartz 250
(Degussa) 11.0% Joncryl 678 6.0% Joncryl 90
______________________________________
The following supplements the descriptions of the water-soluble
polymers used as pigment grinding vehicles for the pigment pastes
or as thickeners to adjust the rheology of the model printing inks
of this patent application.
The water-soluble polymers generally comprise two types: 1.
low-molecular-weight (e.g. as low as 1,000-2,000 up to about
60,000) acrylic solution polymers used as grinding vehicles; 2. low
to high-molecular-weight (e.g. 1,000 up to about 100,000 to
1,000,000 or more) carboxyl-containing polymer emulsions used (as
thickeners) to adjust the rheology of the model printing inks.
The following samples were prepared by solution polymerization for
use primarily as grinding vehicles.
Joncryl 67 (S. C. Johnson)--solid flake; carboxyl-containing
styrene/acrylic resin that dissolves in water upon neutralization;
believed to be styrene/acrylic acid copolymer; MW 10,000; Acid
Number 190; T.sub.g 70.degree. C.; neutralized solution used as a
grinding vehicle;
Joncryl 678/679 (S. C. Johnson)--solid flake; carboxyl-containing
styrene/acrylic acid copolymer that dissolves in water upon
neutralization; contains some alpha-methylstyrene; MW 8000; Acid
Number 200; T.sub.g 85.degree. C.; solution recommended as a
pigment grinding vehicle; also available as an aqueous 35%-solids
solution (Joncryl 61) neutralized with ammonia and containing some
ethylene glycol and isopropanol.
Joncryl 8004--translucent colloidal solution polymer prepared by
solution polymerization and partially-neutralized with ammonia;
32.5% solids; viscosity 50-300 cps; polymer MW 60,000; pH 7.7; Acid
Number 85; Minimum Film Formation Temperature <5.degree. C.;
T.sub.g 21.degree. C.; recommended for use as the sole binder in
water-based flexographic inks for corrugated cardboard, multiwall
paper sacks, and newspaper printing.
Elotex Print 2030 (Elotex AG)--low-viscosity acrylic copolymer
solution; 30% solids (56% water, 14% ethanol); pH 8.9; surface
tension 34 dynes/cm; recommended as a vehicle for printing inks for
poly (vinyl chloride), polyethylene, polypropylene, and polyester
films.
______________________________________ Varnishes 8866 and 9562
(Martin-Huwart) Parts Ingredient Varnish 8866 Varnish 9562
______________________________________ Water 49.20 25.215 Joncryl
90 -- 29.23% Joncryl 679 35.00 25.58 Isopropanol 5.00 4.385
Propylene glycol 2.00 -- Dimethylethanolamine 4.50 -- Aminopropanol
95 -- 1.75 Ammonia (25% aqueous) 4.50 4.385 Anti-foam agent (50%
aqueous) 0.20 0.365 Water -- 9.09 Total 100.40 100.00
______________________________________
To prepare the Varnish 8866, the Joncryl 679 was mixed with the
water and stirred; the isopropanol and propylene glycol were added
slowly with stirring, followed by the dimethylethanolamine and
ammonia to neutralize the Joncryl 679, along with the anti-foam
agent. To prepare the Varnish 9562, the Joncryl 90 was added to the
water with stirring; then, the Joncryl 679, isopropanol, antifoam
agent, aminopropanol, and ammonia were added in that order; the
amount of ammonia was adjusted so as give a pH of 9.2; then, the
second charge of water was added after the Joncryl 90 and Joncryl
679 were completely neutralized. The Varnish 8866 and Varnish 9562
were then used in the model ink formulations.
The following vehicles were prepared by emulsion polymerization
using high concentrations of carboxyl-containing monomers and were
generally intended for use as "thickeners" to control the rheology
of the final printing ink.
Joncryl 90 (S. C. Johnson)--semi-translucent polystyrene emulsion
prepared using as emulsifier a low-molecular-weight alkali-soluble
styrene/acrylic acid copolymer (which is the source of the Acid
Number); 44% solids; viscosity 200 cps; pH 8.2; polymer MW
>200,000; Acid Number 65; Minimum Film Formation Temperature
>86.degree. C.; T.sub.g 110.degree. C.
Joncryl 8050--semi-translucent partially-neutralized acrylic
copolymer (acrylate and methcrylate esters) emulsion using as
emulsifier a low-molecular-weight alkali-soluble styrene/acrylate
copolymer (which is the source of the Acid Number) as well as a
nonionic emulsifier; 42% solids; pH 7.8; viscosity 500 cps; polymer
MW >200,000; Acid Number 91; Minimum Film Formation Temperature,
<-5.degree. C.; T.sub.g -18.degree. C.; recommended as a vehicle
for single-vehicle inks and overprint lacquers.
Joncryl 8051--semi-translucent partially neutralized acrylic
polymer emulsion; 45% solids; viscosity 700 cps; polymer MW
>200,000; Acid Number 83; Minimum Film Formation Temperature
<-5.degree. C.; T.sub.g -23.degree. C.; recommended for
water-based flexographic and gravure inks printed on flexible films
and aluminum foil.
Joncryl SCX 2630--translucent partially-neutralized crosslinked
(with bifunctional acrylate) polymer emulsion using as emulsifier a
low-molecular-weight alkali-soluble styrene/acrylic copolymer
(which is responsible for the Acid Number) as well as a nonionic
emulsifier; 49% solids; pH 8.5; viscosity 1600 cps; T.sub.g
-35.degree. C.; recommended as a water-based low VOC (volatile
organic solvent content ) vehicle for printing on high-slip
low-density polyethylene film.
Joncryl 537 (S. C. Johnson)--carboxyl-containing 40:60
styrene/acrylic copolymer emulsion (acrylic part is a mixture of
acrylate and methacrylate esters) using as emulsifier a
low-molecular-weight alkali-soluble styrene/acrylic copolymer, as
well as anionic and nonionic emulsifiers; 46% solids; viscosity
100-200 cps; pH 9.0 (as neutralized); polymer MW >200,000; Acid
Number 40; dries to form glossy films that combine the fast-dry of
emulsion polymers with the distinctness-of-image and gloss of
water-based alkyd resin films; recommended as both a grinding
vehicle and a letdown vehicle.
Primal E-1941 (Rohm & Haas)--milky-white polymer emulsion;
47.5% solids; pH 7.1; viscosity 1000-3000 cps; Minimum Film
Formation Temperature 37.degree. C.
EXAMPLE 3
Example 1 is repeated except that the toluene is replaced with
equal parts by weight of 2-ethyhexyl acrylate obviating the need,
as required in Example 1, to remove the toluene.
EXAMPLE 4
The polymer composition prepared in Example 3 is used in place of
the Example 1 polymer composition in Examples 2A to 2Z (in Table
1). Satisfactory results are obtained.
EXAMPLE 5
Example 3 is repeated replacing the Novacure of Example 1 with an
equal weight of Novacure 3700-25R, with similar results.
EXAMPLE 6
The polymer composition of Example 5 is used in place of the
Example 1 polymer compositions in Examples 2AA to 2 MM (in Table
1). Satisfactory results are obtained.
EXAMPLE 7
Hydrocarbon Resin Emulsions. These were the hydrocarbon resin
emulsions produced by Exxon Chemical Company under the trade name
"Escorez." The hydrocarbon resins were prepared by cationic
polymerization of a mixture of saturated and unsaturated C4-7
hydrocarbons to give oligomers of varying composition and M.W.'s
above about 2,000 to below about 10,000. The hydrocarbon resins
were then subjected to inverse emulsification with water to give
the hydrocarbon resin emulsions. The solids content of these
emulsions was ca. 53%. Emulsions were prepared of different
hydrocarbon resins, which varied as to their content of aliphatic
and aromatic constituents. The main current application of these
hydrocarbon resin emulsions is as tackifier resins in combination
with acrylate ester copolymer latexes in pressure-sensitive
adhesives.
The hydrocarbon resin emulsion used by applicants was Escorez 9271.
This hydrocarbon resin was made from a petroleum fraction 0f C4-7
hydrocarbons, and contained 70% aliphatic and 30% aromatic
constituents. After the cationic polymerization, the resin
contained an unknown concentration of double bonds, which were not
polymerizable, according to Exxon.
The hydrocarbon resin emulsion had a low surface tension of 27.3
dyne/cm and dried to form a continuous film. The emulsion
coagulated when the photoinitiators, or an organic solvent such as
acetone were added; however, the emulsion could be diluted
indefinitely with distilled-deionized water.
To stabilize the emulsion to the addition of photoinitiator, and to
reduce the solids content to 40% (the concentration used for the
earlier work on water-based ultraviolet light-cured inks), a dilute
solution of an 80/20 mixture of Igepal CO-990FL (formerly GAF; now
Rhone-Poulenc) and Triton X-45 (formerly Rohm & Haas; now Union
Carbide) emulsifiers was added. 2% of this solution was sufficient
to stabilize the emulsion at 40% solids.
Escorez ECR-346R (881030-4) hydrocarbon resin was reported to be
the hydrocarbon resin used to prepare the Escorez 9271 hydrocarbon
resin emulsion. This resin was a brittle yellow solid, similar in
appearance to rosin. It had a density of ca. 0.6 g/cm.sup.3.
10 g. Escorez ECR-346R resin was dissolved in 20 g. toluene to form
a solution, and 5% photoinitiator (based on resin) was added (5%
was used in place of the 2% used earlier to increase the rate of
radical generation upon irradiation). The photoinitiators used were
2,2'-diethoxyacetophenone (Aldrich) or Irgacure 369 (Ciba-Geigy).
10-25% trimethylolpropane triacrylate (UCB Radcure) crosslinking
monomer was added, and the resulting solution was placed on
cleaned-glass plates (rinsed with 10% aqueous sodium hydroxide and
distilled-deionized water, and dried).
When the dried solution was exposed to ultraviolet light (200
watt/in Hanovia lamp; 120 ft/sec belt speed), it cured to an opaque
film. This film was scraped off the glass plate and placed in
toluene. It failed to dissolve in several weeks, indicating that it
was crosslinked. The hydrocarbon resin by itself without the
trimethylolpropane triacrylate dissolved in toluene after
irradiation, indicating that it did not crosslink in the solid
state. The trimethylolpropane triacrylate certainly would have
polymerized in any case, but the hydrocarbon resin was not expected
to polymerize; however, the insolubility of the film combining the
two indicated that the trimethylolpropane triacrylate and the
hydrocarbon resin had copolymerized to form a crosslinked film.
Model ink formulations were prepared using the Escorez 9271
hydrocarbon resin emulsion and evaluated using the following
recipe.
______________________________________ Parts Ingredient Designation
by Weight ______________________________________ Phthalo Blue
Pigment Paste Martin-Huwart P10293*** 34.0 Aqueous Wax Emulsion
Martin-Huwart W6686 8.0 (27% wax) Water-Soluble Polymer* 15.0
Hydrocarbon Resin Emulsion** Exxon Escorez 9271 43.0
______________________________________ *Elotex 2030 (Enorex AG) or
Joncryl SCX2630 (S. C. Johnson) **40% solids; 2% photoinitiator and
10% trimethylolpropane triacrylate based on solids. ***43.48%
Heliogen Blau D7099 AQ/10.87% Joncryl 679/water.
This formulation was rolled out on the surface of high-density
polyethylene, low-density polyethylene, polypropylene,
polycarbonate and aluminum foil films using a Pamarco Handproofer.
The ink films were then exposed to ultraviolet light (Hanovia 200
watt/in lamp; belt speed 120 ft/min) in 1-3 passes without any
preliminary drying; there was little difference in the film
properties as a function of the number of passes.
The adhesion of the cured ink films to the substrate was evaluated
using the Scotch tape test; the mar resistance using the fingernail
scratch test; and the water-sensitivity of the films using the
humidity test. In the Scotch tape test, a 2-3 cm length of Scotch
tape was applied to the ink film and then removed by pulling on the
tape at a right angle to the ink film; the amount of the ink film
removed by the Scotch tape was taken as an indication of the
failure of adhesion. In the mar-resistance test, the ink film was
scratched with a fingernail to determine its resistance to marring.
In the water-sensitivity test, the printed ink films were aged for
72 hours at 100% relative humidity in a desiccator containing
water; the films were then removed, and their adhesion to the
substrate and mar resistance were evaluated. These tests were
empirical, but are representative of the tests used in the
field.
For the polycarbonate film and the aluminum foil, the adhesion to
the substrate and the mar resistance were excellent, both before
and after aging at 100% relative humidity for 72 hours. This
excellent adhesion was attributed, at least in part, to the
relatively polar --O--CO--O-- groups of the polycarbonate. The
surface of the aluminum foil was less well-known and must be
characterized; it may be coated with a thin polymer film.
For the smooth, nonpolar, nonporous high-density polyethylene,
low-density polyethylene, and polypropylene films, the rollouts
were prepared using the Pamarco Handproofer and then exposed
immediately to ultraviolet light (Hanovia 200/watt/in; belt speed
120 ft/min). The ink films on all three polyolefin films gave
excellent adhesion and mar resistance, both before and after aging
at 100% relative humidity for 72 hours. In addition, with the inks
containing the Joncryl SCX-2630 water-soluble polymer, the films
snowed excellent gloss, which has not been seen before with
water-based printing ink films. The success in the polymerization
of these hydrocarbon resins (which had been reported to be
nonpolymerizable) was attributed to the high radical flux arising
from the ultraviolet light irradiation.
EXAMPLE 8
Butadiene/Styrene Copolymer Latexes. This work used a 76.5/23.5
butadiene/styrene copolymer latex (No. R-222 SBR-1 502; Ameripol
Synpol Co.). This latex was typical of those polymerized to ca. 60%
conversion and then coagulated to produce synthetic rubber for
automobile tires. The solids content was low (ca. 18%), and the
particle size was small (ca. 60 nm; capillary hydrodynamic
fractionation). The latex as received contained some chunks of
coagulum, which were filtered out using cotton wool before use.
These copolymers contain residual unsaturation, about one double
bond for each butadiene unit. These double bonds are of several
stereoisomeric configurations, i.e. 65-70% trans-1,4-, 15-20%
cis-1,4-, and 15-20% 1,2-vinyl-.
This SBR-1052 latex was relatively stable at its pH of 8; however,
after storage for several weeks, it tended to cream to form small
chunks floating on the top. Therefore, it was necessary to filter
the latex again with cotton wool before using it in an ink
formulation. The latex solids contents was still 18% after
filtration to remove the cream layer.
Model ink formulations were prepared using the ca. 18%-solids
butadiene/styrene copolymer latex and evaluated using the following
recipe.
______________________________________ Parts Ingredient Designation
by Weight ______________________________________ Blue Pigment Paste
Martin-Huwart P10293 34.0 Aqueous Wax Emulsion Martin-Huwart W6686
8.0 Water-Soluble Polymer Enorex AG Elotex 2030 15.0
Butadiene/Styrene Latex* Ameripol Synpol SBR-1502 43.0
______________________________________ *18% solids; 2%
photoinitiator and 25% trimethylolpropane triacrylate based on
solids
This formulation was rolled out on the surface of high-density
polyethylene, low-density polyethylene, and polypropylene films
using the Pamarco Handproofer. The ink films were then exposed to
ultraviolet light (Hanovia 200 watt/in; belt speed 120 ft/min)
without any preliminary drying for 1-3 passes; there was no
significant differences as a function of the number of passes. The
printability was not very good compared with the earlier samples
because of the low solids content (18%).
The adhesion of the cured ink films to the substrate was evaluated
using the Scotch tape test; the mar resistance using the fingernail
scratch test; and the water-sensitivity of the films using the
humidity test.
For the smooth, nonpolar, nonporous high-density polyethylene,
low-density polyethylene, and polypropylene films, the roll outs
were prepared using the Pamarco Handproofer and then exposed
immediately to ultraviolet light (Hanovia 200/watt/in; belt speed
120 ft/min). The ink films on all three polyolefin films showed
good adhesion and mar resistance, both before and after aging at
100% relative humidity for 72 hours. The abrasion resistance and
washability were good.
EXAMPLE 9
Carboxy-Terminated Polybutadiene. Tests were also run using a
carboxy-terminated polybutadiene oligomer (Scientific Polymer
Products; MW 5.6.times.10.sup.3). This polybutadiene was a viscous
liquid that was soluble in dichloromethane.
2.1 g. of carboxy-terminated polybutadiene were dissolved in 4.2 g.
dichloromethane to give a solution of ca. 33% solids content. 5%
photoinitiator (0.11 g; based on polybutadiene) was added. The
photoinitiators were 2,2'-diethoxyacetophenone (Aldrich) or
Irgacure 369 (Ciba-Geigy). Trimethylolpropane triacrylate (UCB
Radcure) was added to each sample in 0, 10%, and 25% concentration
based or polybutadiene, and the resulting solutions were placed on
glass plates that were cleaned as described earlier to give films
of ca. 1 mm thickness. The glass plates were passed repeatedly for
up to 50 passes under the ultraviolet lamp (Hanovia 200 watt/in;
belt speed 120 ft/min). This irradiation was repeated as rapidly as
possible; the samples were cooled periodically to avoid the buildup
of heat. After irradiation, a piece of film was scraped off the
glass plate and weighed (ca. 0.1 g) and added to dichloromethane
(ca. 3.0 g) to determine if the film was soluble. The results are
given in the following table.
__________________________________________________________________________
Number of Passes Sample Photo-Initiator TMPTMA (%) 10 25 50 Sol.
__________________________________________________________________________
A 2,2'-DEAP 0 ? bubble tack film I* B 2,2'-DEAP 10 ? big bubble
solid film I* C Irgacure 369 0 ? ? tacky film I* D Irgacure 369 10
? film formed solid film I* E Irgacure 369 25 film solid film minor
crack I* F none 0 -- -- -- S*
__________________________________________________________________________
*I = insoluble; S = soluble
The relatively great thickness (ca. 1 mm) required many passes
under the ultraviolet lamp to cure the film. The samples without
trimethylolpropane triacrylate formed a tacky film on the glass
plate, but did not dissolve in dichloromethane. The samples with
trimethylolpropane triacrylate all formed good solid films which
swelled but did not dissolve in dichloromethane. Therefore, it was
concluded that these samples were crosslinked and this
polybutadiene should be emulsified and tested in this form.
Emulsions of this carboxy-terminated polybutadiene are included
with pigment paste, wax and water-soluble polymer as described in
Examples 7 and 8 with similar results.
EXAMPLE 10
______________________________________ Aromatic Urethane-Acrylate
Oligomer (a) Ingredients Parts by weight
______________________________________ Aqueous sodium lauryl
sulfate solution (20 mM) 240.0 Ebecryl 8700 urethane-acrylate
oligomer* 76.8 Trimethylolpropane triacrylate crosslinking monomer
19.2 2-Ethylhexyl acrylate monofunctional monomer 64.0 Hexadecane
coemulsifier 3.26 ______________________________________
*Functionality 2.3; M.W. 1500; viscosity 6000 cps at 65.degree.
C.
2.31 g sodium lauryl sulfate was dissolved in 400.0 g water at room
temperature to give the 20 mM stock solution of emulsifier. The
Ebecryl 6700 and the 2-ethylhexyl acrylate were mixed in a water
bath at about 65.degree. C. to reduce the high viscosity of the
oligomer. This lower-viscosity mixture was removed from the water
bath, and the trimethylolpropane triacrylate and hexadecane were
added and mixed to form the oil phase. This oil phase was added to
the aqueous 20 mM sodium lauryl sulfate solution and mixed in a
beaker with a magnetic stirrer for 30 minutes to form a crude
emulsion. This emulsion was stirred in the Omni-Mixer at 16,000 rpm
for 90 seconds and then subjected to ultrasonification for one
minute to reduce the average droplet size to submiscopic size. To
50.0 g of this emulsion was added 0.40 g (2%)
2,2'-diethoxyacetophenone photoinitiator and the mixture was
tumbled end-over-end in a capped bottle for one hour until the
photoinitiator was completely mixed with emulsion.
(b) This Ebecryl 6700 emulsion was employed in the following model
ink formulation in accordance with this invention:
______________________________________ Ingredients Parts by Weight
______________________________________ Blue pigment paste P10293
6.8 Ebecryl 6700 urethane-acrylate emulsion 8.6 Aqueous Wax
emulsion 6686/B (27% wax) 1.6 Elotex 2030 water-soluble polymer 3.0
______________________________________
This model ink was drawn down on plastic film substrates and
immediately exposed to ultraviolet light (Hanovia; 200 watt/in) at
150 foot/min. After one pass, the adhesion was very good for the
low-density polyethylene and polypropylene, but poorer for
high-density polyethylene. After three passes, the adhesion was
excellent on all three substrates.
(c) The following formulation using Joncryl 8051 instead of the
Elotex 2030 in (b) above gave similar results.
______________________________________ Ingredient Parts by Weight
______________________________________ Blue pigment paste P10293
6.8 Ebecryl 6700 urethane-acrylate emulsion 9.6 Aqueous Wax
emulsion 6686/B 1.0 Joncry 8051 water-soluble polymer 2.6 (d) The
following formulation (3 parts) was used instead of the Elotex 2030
in (b) above. Elotex 2030 40.0 Water 3.0 Aqueous ammonia (28%) 1.0
Acrysol RM-5 (Rohm & Haas) 2.0
______________________________________
The Acrysol RM-5 was added to the rest of the mixture with
stirring, to give a very viscous, smooth solution. The adhesion to
the plastic film substrates was improved.
Acrysol RM-5 is an associative thickener used as a viscosity
modifier in the inks of this invention. "Associative thickener" is
a term applied to water soluble or water dispersible polymers the
molecules of which associate with each other in aqueous solution or
dispersion, to give the requisite rheological properties. Thus,
these thickeners depend less on specific interactions with the
functional groups on the latex particles and give the same
rheological properties with all latexes, independent of their type
and composition.
This Acrysol RM-5 is a milky white liquid of 30% solids content,
100 cps Brookfield viscosity (#1 spindle, 60 rpm), and pH 2.2-3.2
presumably prepared by emulsion polymerization using
carboxyl-containing monomers.
It is used after neutralization to pH 8.0-8.5, and reportedly has a
higher high-shear-rate viscosity and a lower low-shear-rate
viscosity (and thus should show a smaller overall decrease in
viscosity with increasing shear rate).
Following are further experiments using different oligomers with
vinyl functionality.
Oilgomers with Vinyl Functionality
EXAMPLE 11
Carboxyl-terminated polybutadiene (Scientific Polymer Products;
1.9% Carboxyl content; 11/12/87, Catalog #524 CAS #68891-79-2; MW
ca. 5700). The crosslinking of this oligomer from organic solvent
solution in presence of trimethylolpropane triacrylate is described
earlier in Example 9. The present experiments describe the
crosslinking from aqueous emulsion as in the present invention.
EXAMPLE 12
Aromatic Urethane Acrylate Oligomer: Ebecryl 220 resin
(multifunctional aromatic urethane acrylate containing an acrylated
polyol; functionality 6, MW 800; viscosity 28000 cps at 25.degree.
C.; Tg 49.degree. C.; combines fast cure with excellent hardness
and solvent resistance).
EXAMPLE 13
Aliphatic Urethane Acrylate Oligomer: Ebecryl 230 resin (aliphatic
urethane diacrylate; functionality 2; MW 5000; viscosity 40000 cps
at 25.degree. C.; Tg -55, -39; cures to soft, flexible film).
EXAMPLE 14
Acrylic Oligomer: Ebecryl 745 (acrylic oligomer diluted with 46%
monomer blend: viscosity 30000 cps at 25.degree. C.; T.sub.g
30.degree. C.; designed to give improved adhesion to difficult
substrates).
EXAMPLE 15
Polyester Acrylate Oligomer: Ebecryl 810 (multifunctional polyester
acrylate; functionality 4; MW 1000; viscosity 550 cps at 25.degree.
C.; acid value 17; T.sub.g 31.degree. C.; general-purpose
fast-curing resin with low viscosity).
Monofunctional Monomer
ODA: octyl/decyl acrylate mixture of monofunctional monomers of
linear eight and ten carbon acrylate esters.
Preparation of the Miniemulsions
The miniemulsions were prepared by stirring the oil phase
containing the Ebecryl 810, hexadecane, trimethylolpropane
triacrylate, and 2-ethylhexyl acrylate into the aqueous phase
containing the sodium lauryl sulfate, and then subjecting this
crude emulsion in 50 ml portions to ultrasonification
(Ultrasonifier Model W-350, Branson Sonic Power). The Ebecryl 810
was used because of its low viscosity.
Table I gives the recipe used in these experiments.
TABLE 1 ______________________________________ Recipe for
Preparation of Miniemulsions Ingredient Parts by Weight
______________________________________ Water containing 20 mM
sodium lauryl sulfate 160.07 Ebecryl 810 resin 51.49 Hexadecane
2.19 Trimethylolpropane triacrylate 12.91 2-Ethylhexyl acrylate
42.83 ______________________________________
Table II gives the average particle size measured by photon
correlation spectroscopy (Nicomp). There was little difference in
the average particle size measured initially. An ultrasonification
time of 4 minutes was selected because this time ensured that the
ultrasonification was complete; moreover, the distribution at 4
minutes was narrower than at the earlier times.
TABLE II ______________________________________ Particle Size of
Ebecryl 810 Miniemulsions Ultrasonification Initial Particle Size
After 96 Hours Time (min) (nm) (nm)
______________________________________ 1 260 437 2 241 387 4 241
378 8 234 377 ______________________________________
Table III gives the recipes for the miniemulsions. The aqueous
stock solution containing 20 mM sodium lauryl sulfate was prepared.
Then, the oil phase containing the oligomer, hexadecane,
trimethylolpropane triacrylate, and 2-ethylhexyl acrylate (or the
octyl/decyl acrylate mixture in one case) was stirred into the
water phase using a magnetic stirrer to make the crude emulsion.
The crude emulsion was then subjected to ultrasonification for 4
minutes (50% duty cycle, power level 7).
TABLE III
__________________________________________________________________________
Recipes for the Miniemulsions Water* Oligomer HD** TMPTA***
2-EHA**** Ex. Oligomer (g) (g) (g) (g) (g)
__________________________________________________________________________
11 Polybutadiene 80.01 25.60 1.10 6.41 21.30 12 Ebecryl 220 80.00
25.72 1.11 6.47 21.29 13 Ebecryl 230 80.01 25.64 1.09 6.39 21.70 14
Ebecryl 745 80.02 25.52 1.09 6.40 21.50 15 Ebecryl 810 160.07 51.49
2.19 12.91 42.83 12a Ebecryl 220***** 80.01 25.57 1.09 6.44 21.30
__________________________________________________________________________
*water containing 20 mM sodium lauryl sulfate **hexadecane
***trimethylolpropane triacrylate ****2ethylhexyl acrylate
*****used ODA monomer in place of 2ethylhexyl acrylate
Printing on Plastic Film
The photoinitiator was then added; 2% of 2,2'-diethoxyacetophenone
based on oil phase was added to each miniemulsion, and the samples
were tumbled in capped bottles for one hour at room temperature to
allow the photoinitiator to swell the oligomer emulsion
particles.
Table IV gives the recipes for the model inks. All of the
miniemulsions were formulated with the P10293 Blue Pigment Paste,
wax emulsion 6686/B, and the Elotex 2030 water-soluble polymer used
to adjust the rheology. The model inks were then rolled out on
high-density polyethylene, low-density polyethylene, and
polypropylene films using the Pamarco handproofer and cured by
passing on a belt moving at 130 ft/min under the Hanovia 200
watt/inch lamp.
TABLE IV ______________________________________ Formulation for
Model Inks Ingredients (g) Parts by Weight
______________________________________ Blue Pigment Paste P10293
6.8 34.0 Aqueous Wax Emulsion 6686/B 1.6 8.0 Elotex 2030 3.0 15.0
Miniemulsion 8.6 43.0 ______________________________________
The cured ink films on the plastic film substrates were then tested
for adhesion using the scotch tape test after one and three passes
under the ultraviolet lamp, for mar resistance using the fingernail
test, and for water resistance after aging for two days at high
humidity. Table V gives the test results.
Overall, the Ebecryl 745 showed the best results among the resins
tested in this series. It showed very good adhesion on all three
plastic films using the Scotch tape tests. Ebecryl 230 showed
excellent adhesion to the polypropylene film. All of the other
resins showed reasonably acceptable results.
TABLE V ______________________________________ Ink Film Adhesion,
Mar Resistance, and Water Resistance HDPE* LDPE** PP***
______________________________________ Polybutadiene Example 11
Printability good good fair Scotch tape 1 pass poor-fair poor-fair
fair 3 passes poor-fair poor-fair fair Mar resistance poor fair
good Water resistance very good fair fair Ebecryl 220 - Example 12
Printability good fair fair Scotch tape 1 pass fair poor fair 3
passes good fair good Mar resistance very good good good Water
resistance poor poor good Ebecryl 230 - Example 13 Printability
good fair poor Scotch tape 1 pass good fair excellent 3 pases good
fair excellent Mar resistance very good very good very good Water
resistance good good good Ebecryl 745 - Example 14 Printability
good good good Scotch tape 1 pass good fair very good 3 passes very
good-excel. good very good-excel. Mar resistance good very good
very good Water resistance very good very good very good Ebecryl
220/ODA- Example 12a Printability good good good Scotch tape 1 pass
poor fair good 3 passes poor good very good mar resistance poor
fair good Water resistance very good poor good Ebecryl 810 -
Example 15 Printability very good fair fair Scotch tape 1 pass
poor-fair poor poor 3 passes poor-fair poor poor Mar resistance
poor poor poor Water resistance poor poor poor
______________________________________ *high-density polyethylene
**lowdensity polyethylene ***polypropylene
This invention has been disclosed with respect to preferred
embodiments thereof and it will be understood that modifications
and variations obvious to those skilled in the art are to be
included within the spirit and purview of this application and the
scope of the appended claims.
The terms "UV" and "M.W." (or "MW") appearing herein and in the
appended claims signify, respectively, "ultra-violet radiation" and
"molecular weight." The terms "monofunctional monomer" and
"polyfunctional monomer" appearing herein and in the appended
claims signify, respectively, "monoethylenically unsaturated
monomer" and "polyethylenically unsaturated monomer".
* * * * *